The present invention relates to a process for the manufacture of a polyurethane foam by reaction of a polyol with a polyisocyanate, in which process a tertiary amine is used as catalyst and in which process an expansion agent or foaming agent, such as water, for example, is used.
It is well known to use one or more tertiary amines to catalyze a first reaction: that of at least one polyol with at least one polyisocyanate. Furthermore, in the case where water is used as foaming agent, the tertiary amine(s) is (are) capable of catalyzing a second reaction: that of water with the free isocyanate functional groups, which reaction results in the evolution of carbon dioxide gas which serves for the expansion of the foam. Several known techniques exist for the preparation of polyurethanes. According to a first technique, at least one polyetherpolyol and/or at least one polyesterpolyol is reacted with at least one polylisocyanate, so as to obtain a prepolymer comprising free isocyanate groups, and then the prepolymer obtained is reacted with an additional amount of polyol(s). Another well known technique is the so-called xe2x80x9cone shotxe2x80x9d technique, where all the ingredients are introduced, separately or selectively premixed according to their compatibility, into the mixing head.
The known tertiary amines can promote the first reaction and/or the second reaction to variable extents. When one of the reactions is not catalyzed or is insufficiently catalyzed, it is then necessary to use another catalyst for the other reaction. This other catalyst can be an organometallic derivative, such as stannous octoate or dibutyltin dilaurate, known for preferentially catalyzing the isocyanate polyol reaction. The use is therefore being attempted of tertiary amines which satisfactorily catalyze both reactions. It is known to use tertiary amines, such as N-ethylmorpholine, dimethylbenzylamine, triethylene-diamine and hexadecyldimethylamine, these tertiary amines being introduced as such into the reaction mixture.
However, these tertiary amines have a disadvantage: they are volatile, have a very unpleasant amine smell and are often toxic. As most of the tertiary amine(s) remains in the foam in the free state, the foam prepared has an undesirable smell and gives off toxic vapors. Furthermore, the handling of tertiary amines during the manufacture of polyurethane foam demands specific precautions in order to meet safety standards.
In order to overcome the above disadvantages, the use has been proposed (paper by Savoca, Franson and Louie, UTECH""92 Conference Proceedings, p. 309-315 and U.S. Pat. No. 4,433,170) of less volatile amines with a high molecular weight, however, the ratio by weight of the tertiary amine functional group with respect to the weight of the molecule becomes low and the reactivity of the catalyst decreases. Furthermore, these amines are more expensive, they often still have an unpleasant smell and they often have a reactivity which is too different from that of standard amines, which is not very acceptable to foam producers.
Furthermore, it has also been proposed (paper by Diblitz and Hoell, UTECH""92 Conference Proceedings, p. 80-85) to attach the tertiary amine catalyst to free isocyanate functional groups. To this end, a tertiary amine, for example a hydroxylated tertiary amine, which reacts with the isocyanate functional groups during the preparation of the polyurethane is added to the reaction mixture. However, in this case, it is still necessary to handle polluting amines at the stage of preparation of the foam and precautions are still necessary to meet safety standards.
The preparation of a polyurethane by reaction of at least one polyesterpolyol with at least one polyisocyanate is well known. This polyesterpolyol is conventionally prepared by reaction of an acid reactant having a functionality at least equal to 2, such as adipic acid, with at least one polyol with a functionality equal to 2, such as diethylene glycol, subsequently denoted by P2, and at least one polyol with a functionality at least equal to 3, such as trimethylolpropane, glycerol or pentaerythritol, subsequently denoted by P3. FR-A-2 747 389 discloses the manufacture of specific polyesterpolyols, capable of being used in the manufacture of polyurethane foams, which do not exhibit fogging when they are used in the passenger compartment of a vehicle. According to this patent, the polyol P2 comprises monoethylene glycol and optionally a branched glycol with a functionality equal to 2 and the polyol P3 is a polyoxyalkylenated polyol which is, inter alia, obtained from triethanolamine or from triisopropanolamine. In the preparation of the polyurethane foams disclosed in FR-A-2 747 389, a separate tertiary amine catalyst, dibutylbenzylamine according to the examples, is still added.
According to the present invention, it has been found that, when the polyesterpolyol is prepared from at least one polyol P3 which is a polyoxyalkylenated polyol obtained by oxyalkylenation of a tertiary polyalkanolamine and when it is thus xe2x80x9caminexe2x80x9d, it is no longer essential, during the manufacture of the polyurethane foam, to separately add a tertiary amine as catalyst or, that to say the least, the amount of separate tertiary amine to be added is markedly reduced. This is because it has been found that the amine polyesterpolyol defined above has an autocatalytic effect, that is to say that it has both a reactive role and a catalyst role.
Throughout the text of the present patent application, the term xe2x80x9cpolyalkanolaminexe2x80x9d has generically denoted an alkanolated amine which can be either a polyalkanolmonoamine or a polyalkanolpolyamine.
In a first embodiment, the tertiary polyalkanolamine is a polyamine, at least one amine group and preferably all the amine groups of which is (are) tertiary and is (are) substituted by identical or different C1-C6 alkanol radicals.
In a second embodiment, the tertiary polyalkanolamine is a tertiary monoamine substituted by identical or different C1-C6 alkanol radicals.
Generally, according to the present invention, it has been found that an amine polyesterpolyol in which is inserted at least one such polyoxyalkylenated polyalkanolamine had, by itself, a catalytic effect for the formation of polyurethane foams. It acts mainly on the foaming reaction in the presence of water and to a certain extent on the reaction of the polyol with an isocyanate, known as gelling. Consequently, it is possible not to use any other amine catalyst, only a small amount of catalyst of the organometallic type optionally being able to be added in order to accelerate the gelling reaction and to obtain a foam which does not collapse.
According to the invention, the tertiary amine is introduced during the polyesterification process into at least one polyesterpolyol used for the manufacture of the polyurethane: it is thus included or inserted in the said polyesterpolyol; the result of this is that:
the risks of evolution of tertiary amine during the manufacture of the polyurethane are avoided and, consequently, there is neither a problem of odor nor a problem of toxicity on the foam production site; problems of pollution during the production of the foam are thus avoided and certain specific precautions for meeting safety standards do not have to be taken;
foams are obtained which do not have an amine smell and are less toxic. In particular, a source of fogging when the foam is used in the passenger compartment of a motor vehicle is thus avoided and, furthermore, when polyesterpolyols, such as those disclosed in FR-A-2 747 389, not comprising volatile cyclic dimers are employed, the foam does not result in any fogging.
The subject matter of the present invention is consequently a process for the manufacture of a polyurethane foam by reaction of at least one polyesterpolyol and of at least one polyisocyanate in the presence of a foaming agent and of a catalyzing agent, such a polyesterpolyol having been obtained beforehand by reaction of an acid reactant A, comprising at least one aliphatic or aromatic polyacid with a functionality at least equal to 2, with at least one polyol P2 with a functionality equal to 2 and at least one polyol P3 with a functionality at least equal to 3 and subsequently being denoted by AP2P3, characterized in that the catalyzing agent is at least partially composed of at least one amine polyesterpolyol AP2P3, in which at least a portion of the polyol P3 is composed of at least one polyoxyalkylenated polyalkanolamine having at least one tertiary amine functional group, the alkanol radicals of the said polyalkanolamine being C1-C6 radicals, the alkylene oxide units being C2-C4 units and the statistical mean of the number N of alkylene oxide units per polyoxyalkylated polyalkanolamine molecule being equal to fxc3x97x, f being the number of hydroxyl functional groups per polyalkanolamine molecule and x being a number between 1 and 10 inclusive, preferably between 2 and 5.
The foaming agent is preferably water.
According to the invention, preferably no amine catalyst other than the amine polyesterpolyol AP2P3 is used. However, it can be advantageous to also add a nonamine catalyst of organometallic type, such as stannous octoate or dibutyltin dilaurate, in order to accelerate the gelling reaction of the isocyanate with the polyol and thus to obtain a more stable foam.
The polyalkanolamine can advantageously be a polyamine, all the amine functional groups of which are tertiary; however, in a particularly preferred way, the polyalkanolamine is a tertiary monoamine.
Preferably, the alkanol radicals of the polyalkanolamine(s) are C2-C3 radicals and the alkylene oxide units are taken from the group formed by ethylene oxide, propylene oxide and their mixtures, x being any number between 2 and 5 inclusive.
In the amine polyesterpolyol AP2P3, the molar ratio of the polyoxyalkylenated polyalkanolamine(s) to all the other polyols used for the reaction with the acid reactant A is preferably between 1/99 and 50/50, with greater preference between 3/97 and 10/90 (proportions in moles).
The polyol P2 comprises at least one glycol chosen from the group formed by monoethylene glycol, diethylene glycol and polyethylene glycols with an order greater than 2; it can also comprise at least one branched glycol of formula: 
in which formula:
R0 represents, independently in each [R1R0R2] unit, a carbon atom, a C6 alicyclic radical, a phenyl radical or a heterocyclic radical comprising 4 to 6 atoms which is saturated or unsaturated, the heteroatom being O or N;
R1 and R2 represent, independently in each [R1R0R2] unit and independently of one another, a hydrogen atom, a linear C1-C6 alkyl radical, a branched C3-C6 radical, a C6 alicyclic radical or an aryl radical;
with the proviso that, if R0 is not a ring in any of the [R1R0R2] units, R1 and/or R2 is (are) different from H in at least one of the [R1R0R2] units;
n is an integer between 1 and 8 (inclusive), with the proviso that, if n is greater than or equal to 4, the number of the carbon atoms in the combined R0, R1 and R2 radicals is greater than 8 in total.
Advantageously, tile polyol P3 is composed entirely of one or more polyoxyalkylenated polyalkanolamine(s); however, it can also comprise at least one polyoxyalkylenated polyalkanol obtained by oxyalkylenation form a hydroxylated component, such as trimethylolethane, trimethylolpropane, ditrimethylol-propane, pentaerythritol, dipentaerythritol, glycerol, hexane-1,2,6-triol, butane-1,2,4-triol, sorbitol, tris(2-hydroxyethyl) isocyanurate and their mixtures, the number of alkylene oxide units per hydroxyl functional group of the polyalkanol preferably being, as a statistical mean, between 1 and 10 inclusive. The polyol P3 can also comprise non-oxyalkylenated alkanols, such as trimethylolethane, trimethylol-propane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, glycerol, hexane-1,2,6-triol, butane-1,2,4-triol, sorbitol, tris(2-hydroxyethyl) isocyanurate and their mixtures.
The acid reactant A comprises at least one aliphatic or aromatic diacid preferably taken from the group formed by adipic acid and phthalic anhydride; it can also comprise at least one branched acid having a functionality greater than or equal to 2, which branched acid is preferably a dimer of an unsaturated C17-C24 fatty acid. Use is advantageously made of a C18 fatty acid mono-, di- and trimer mixture comprising at least 70% by weight of dimer.
For the preparation of the amine polyesterpolyol AP2P3, the acid reactant A is conventionally reacted with a total amount of polyols P2 and P3 greater than stoichiometry, so as to obtain an amine polyesterpolyol AP2P3 comprising at least two free hydroxyl groups per molecule. The reaction is generally carried out under an inert atmosphere, at a temperature of between 160 and 250xc2x0 C., in the presence of an appropriate metallic or organometallic catalyst.
The polyurethane foam is prepared by reaction of at least one polyesterpolyol and of at least one polyisocyanate by any known process, in particular by the so-called xe2x80x9cone shotxe2x80x9d process. The processes for the manufacture of polyurethanes are described in J. H. Saunders, K. C. Frisch, High Polymers, 1964, Vol. 26, entitled xe2x80x9cPolyurethanes Chemistry and Technologyxe2x80x9d, published by xe2x80x9cInterscience Publishersxe2x80x9d, or in G. Woods, 1982, xe2x80x9cFlexible Polyurethane Foams: Chemistry and Technologyxe2x80x9d, published by xe2x80x9cApplied Science Publishersxe2x80x9d.
Other additives can also be introduced in a known way into the reaction mixture, such as surfactants, polyols with a low molecular weight of less than or equal to 400 as chain extenders, foam-stabilizing agents, flame-retardant agents, pigments, dyes, fillers, stabilizers against aging or substances having a fungistatic or bacterioszatic effect.
The polyisocyanate used can conventionally be at least one aromatic, aliphatic or heterocyclic polyisocyanate. Use is generally made of polyisocyanates or mixtures of polyisocyanates which are readily available commercially, such as 2,4- and 2,6-toluylene diisocyanate (TDI) and their mixtures, diphenylmethane diisocyanates (MDI) or prepolymers resulting from the partial reaction of a polyisocyanate with a hydroxylated compound.
Another subject matter of the invention is an amine polyesterpolyol AP2P3 capable of being used in the process defined above, the said polyesterpolyol being obtained by reaction of an acid reactant A, comprising at least one aliphatic or aromatic polyacid with a functionality at least equal to 2, with at least one polyol P2 with a functionality equal to 2 and at least one polyol P3 with a functionality at least equal to 3, a least a portion of the polyol P3 being composed of:
at least one polyoxyalkylenated tertiary polyalkanolmonoamine, the alkanol radicals of the said polyalkanolmonoamine being C1-C6 radicals, the alkylene oxide units being C2-C4 units and the statistical mean of the number of alkylene oxide units per hydroxyl functional group of the polyalkanolmonoamine being between 1 and 10 inclusive, the polyol P2 in this case not comprising monoethylene glycol, or
at least one polyoxyalkylenated polyalkanolpolyamine having at least one tertiary amine functional group, the alkanol radicals of the said polyalkanolpolyamine being C1-C6 radicals, the alkylene oxide units being C2-C4 units and the statistical mean of the number N of alkylene oxide units per polyalkanolpolyamine molecule being equal to f less than x, f being the number of hydroxyl functional groups per polyalkanolamine molecule and x being a number between 1 and 10 inclusive; in this case, preferably all the amine functional groups of the polyamine are tertiary.
The alkanol radical of the polyalkanolamine(s) is preferably a C2-C3 radical and the alkylene oxide unit is taken from the group formed by ethylene oxide, propylene oxide and their mixtures.
The molar ratio of the polyoxyalkylenated polyalkanolamine to all the other polyols used for the reaction with the acid reactant A is advantageously between 1/99 and 50/50, preferably between 3/97 and 10/90 (proportions in moles).
When the polyalkanolamine is a polyalkanolmonoamine, the polyol P2 advantageously comprises at least one glycol chosen from the group formed by diethylene glycol and polyethylene glycols with an order greater than 2.
When the polyalkanolamine is a polyalkanolpolyamine, the polyol P2 advantageously comprises at least one glycol taken from group formed by monoethylene glycol, diethylene glycol and polyethylene glycols with an order greater than 2.
In all cases, the polyol P2 can also comprise at least one branched glycol of formula: 
in which formula:
R0 represents, independently in each [R1R0R2] unit, a carbon atom, a C6 alicyclic radical, a phenyl radical or a heterocyclic radical comprising 4 to 6 atoms which is saturated or unsaturated, the heteroatom being O or N;
R1 and R2 represent, independently in each [R1R0R2] unit and independently of one another, a hydrogen atom, a linear C1-C6 alkyl radical, a branched C3-C6 radical, a C6 alicyclic radical or an aryl radical;
with the proviso that, if R0 is not a ring in any of the [R1R0R2] units, R1 and/or R2 is (are) different from H in at least one of the [R1R0R2] units;
n is an integer between 1 and 8 (inclusive), with the proviso that, if n is greater than or equal to 4, the number of the carbon atoms in the combined R0, R1 and R2 radicals is greater than 8 in total.
The polyol P3 is preferably composed entirely of one or more polyoxyalkylenated polyalkanolamine(s) However, the polyol P3 can also comprise at least one polyoxyalkylenated polyalkanol obtained by oxyalkylenation from a hydroxylated component, such as trimethylolethane, trimethylolpropane, ditrimethylol-propane, pentaerythritol, dipentaerythritol, glycerol, hexane-1,2,6-triol, butane-1,2,4-triol, sorbitol, tris(2-hydroxyethyl) isocyanurate and their mixtures, the number of alkylene oxide units per hydroxyl functional group in the molecule being, as a statistical mean, between 1 and 10 inclusive. The polyol P3 can also comprise a non-oxyalkylenated polyol, such as trimethylolethane, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipenta-erythritol, glycerol, hexane-1,2,6-triol, butane-1,2,4-triol, sorbitol, tris(2-hydroxyethyl) isocyanurate and their mixtures.
The acid reactant A advantageously comprises at least:
one aliphatic or aromatic diacid preferably taken from the group formed by adipic acid and phthalic anhydride, and/or
one branched acid having a functionality greater than or equal to 2, which branched acid is preferably a dimer of an unsaturated C12-C24 fatty acid.
Another subject matter of the invention is the polyurethane foams obtained by the process defined above. These polyurethane foams can be used in all their known uses. Mention may be made of heir use in the furniture industry, for the manufacture of mattresses, cushions and coverings, for the manufacture of cushions and armrests in vehicles, and as absorbent for mineral oils. When they are rigid, they can be used as thermal and sound insulators in buildings, as shockproofing in packages, as filters and; for their buoyancy, in shipbuilding. More particularly, a subject matter of the invention is the use of these foams for the production of components intended to equip the passenger compartment of a motor vehicle.
Several examples of the implementation of the process according to the invention will be given below, purely by way of illustration and without limitation.